SURFACE STUDIES ON UNTREATED AND PLASMA-TREATED CARBON-FIBERS

XPS and contact-angle measurements have been performed on a number of untreated and plasma-treated commercial carbon fibers. In the case of untreated unsized fiber, correlations between surface composition, modulus and wettability were observed. Sized fibers had similar surface compositions and contact angles. Plasma treatment resulted in decisive improvements in wettability. Sized fibers underwent hydrophobic recovery as a result of segmental motions within the sizing layer. Unsized fibers did not change their wettability upon aging in air, while dramatic increases in advancing angles and decreases in surface-oxygen composition were observed upon aging in water, possibly owing to treatment-induced solubilization of oxidized species.